This invention relates to train handling apparatus and, more specifically, to apparatus for indexing a train through a work station one or more cars at a time while the cars remain coupled.
Unit trains, usually comprising 100 or more cars of identical size, are recognized as efficient carriers of bulk raw materials, such as coal, iron ore, limestone, and liquid or dry chemicals. Of major concern in systems employing unit trains are the speed and reliability of equipment for handling such trains at work areas where they are loaded or unloaded. U.S. Pat. No. Reissue 27,300, for example, discloses railroad car handling apparatus which is adapted to automatically index a unit train through a rotary car dumper or other equipment for filling or emptying a car or a limited number of cars at a time. Various techniques for holding a train and indexing the train are used in addition to wheel chocks disclosed in the aforementioned patent. Wheel chocks, while providing adequate service in most installations, are inherently limited in their capacity for holding a train when the car with which they are engaged is empty, since the car, when driven by a heavy load, has a tendency to roll up over the chocks. Moreover, extremely high coupler loading on a chocked car may cause structural damage to the suspension area of the car's undercarriage.
Apparatus for stooping or otherwise locating a railroad car are shown in U.S. Pat. Nos. 2,017,392 to Blake and 3,220,576 to Cheek, showing stop arms pivotal in a vertical plane. U.S. Pat. Nos. 2,945,606 to Musschoot et al, and 3,799,064 to Kikuchi et al, are representative of devices for engaging a coupler which are retractable and/or operated from under the trackway. Such devices are typically limited to use with uncoupled car ends.
An improved train positioner is set forth in U.S. Pat. No. 4,006,691. According to the teachings of that patent, a train position control arm is provided which is adapted to engage a car by its coupler and which has certain features which are advantageous both in stationary train holding apparatus and with a traveling carriage of a train positioner. A car is advanced by the traveling train positioner arm, and when the car is advanced to its proper position, a train holding arm is lowered to engage a coupling. After the stationary arm is lowered, the traveling arm is raised and is retracted to a new position and then the stationary arm is raised. Some of the vertical movements of the stationary and movable arms are obviously outside of the indexing cycle and the dump cycle and tend to add time onto the entire dumping operation.